After cleared for a visual approach the flight crew of a B737-700 descended below the floor of the c...

Narrative:

Evening VMC; unlimited visibility; both pilots had airport in sight; and informed approach. Approach gave us a 230 heading; cleared for a visual approach 26. I recall being at or above 5000 MSL at time of clearance and the captain put 3;000 in the altitude window; and asked if I saw it and concurred. I looked down at the map display; saw the assigned heading/course would take us just outside the fix from which the captain had extended the final course. It had an at/above 3000 restriction; and; given our altitude and distance from the fix I figured that would work out fine. I went heads out; looking for traffic. Next; I made the '4000 for 3000' call and; shortly thereafter; approach called to let us know we were below the class B floor of 4000. I acknowledged and the captain climbed back up to 4000. Rest of the approach was normal. We could have referred to the class B chart though--when off segment; and going 210 KTS--by the time we determined our position relative to the chart; we might have stayed too high too long for a stable approach. Given our off-segment position; and ATC's familiarity with the local area; ATC could have helped by stating 'maintain 4;000 ft until X miles from the runway; cleared for the visual'.

Original NASA ASRS Text

Title: After cleared for a visual approach the flight crew of a B737-700 descended below the floor of the Class B at PHX. They were alerted by Approach Control and climbed to comply.

Narrative: Evening VMC; unlimited visibility; both pilots had airport in sight; and informed approach. Approach gave us a 230 heading; cleared for a visual approach 26. I recall being at or above 5000 MSL at time of clearance and the Captain put 3;000 in the ALT window; and asked if I saw it and concurred. I looked down at the map display; saw the assigned heading/course would take us just outside the fix from which the Captain had extended the final course. It had an at/above 3000 restriction; and; given our altitude and distance from the fix I figured that would work out fine. I went heads out; looking for traffic. Next; I made the '4000 for 3000' call and; shortly thereafter; approach called to let us know we were below the Class B floor of 4000. I acknowledged and the Captain climbed back up to 4000. Rest of the approach was normal. We could have referred to the Class B chart though--when off segment; and going 210 KTS--by the time we determined our position relative to the chart; we might have stayed too high too long for a stable approach. Given our off-segment position; and ATC's familiarity with the local area; ATC could have helped by stating 'maintain 4;000 FT until X miles from the runway; cleared for the visual'.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	916693
Time
Date	201010
Local Time Of Day	1801-2400
Place
Locale Reference	PHX.Airport
State Reference	AZ
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	First Officer Pilot Not Flying
Experience	Flight Crew Last 90 Days 244 Flight Crew Type 5300
Person 2
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 11 Flight Crew Type 8000
Events
Anomaly	Airspace Violation All Types Deviation - Procedural Published Material / Policy Deviation - Procedural FAR

After cleared for a visual approach the flight crew of a B737-700 descended below the floor of the class B at phx. They were alerted by approach control and climbed to comply.